Information on 'Virtual Colonoscopy'

Dear OncoLink "Ask the Experts,"
Can you give me any information on the "virtual colonoscopy"?
Thanks,
M.H.

Richard Whittington, MD, Associate Professor of Radiation Oncology at the University of Pennsylvania School of Medicine, responds:

Virtual colonoscopy is currently being developed. It is a series of ultrathin CT scan images that are stacked by a computer and then the large intestine is isolated. It is currently investigational, as the early data from a few centers has suggested that it may be nearly as effective in their hands as conventional colonoscopy. It is time consuming since it may involve 100 to 250 CT slices, and the images need to be manipulated after they are obtained. In institutions that do these studies, the patients currently undergo conventional colonoscopy as well to determine the accuracy of the virtual study. All of the centers doing the study have shown that there is a very steep learning curve. The test is least sensitive in detecting villous adenomas, and they are the polyps most likely to contain cancers. It is still necessary to take the bowel prep; only it needs to be more effective than is needed for colonoscopy. Also, due to its experimental nature, insurance companies may not currently reimburse the procedure.